THE OCEAN FLOORS AND BELOW. EARTH2CLASS WORKSHOPS FOR TEACHERS at LAMONT-DOHERTY EARTH OBSERVATORY Originally Presented January 24, 2004. Guest Scientist: Gerard Iturrino: “The Structure and Composition of the Ocean Crust”.
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EARTH2CLASS WORKSHOPS FOR TEACHERS at LAMONT-DOHERTY EARTH OBSERVATORY
Originally Presented January 24, 2004
In today’s program, we will first review how we learned what lies hidden beneath the oceans on the sea floor. Then, Dr. Iturrino will explain the investigations that he and others conduct into what lies hidden under the sea floors in the oceanic crust.
To measure depth, they dropped lead-weighted lines overboard to determine how many fathoms (6 feet) or other depths of water lay beneath the keel.
Side note: Sam Clemens took his pen name—Mark Twain—in part from the leadsman cry meaning 12 feet deep
First efforts before the Civil War were unsuccessful, but in 1869, the first trans-Atlantic telegraph cable linked North America and Europe, opening a new age in communication.
One of the main reasons for this voyage was to learn more about the sea floors so other cables could be laid down. Like all vessels up till then, HMS Challenger determined depth by dropping a weighted line. Her approximate measurements permitted the first general understanding of the topography of the ocean bottoms.
In this way, we learned that there are great mountain ranges, deep trenches, flat abyssal plains, volcanoes, and many other features hidden beneath the waves. .
There are several basic “zones”:
continental margin/abyssal plains/MOR/ abyssal plains/continental margin
In the 1940s, Jacques-Yves Cousteau and colleagues in the French Navy invented SCUBA (Self-Contained Underwater Breathing Apparatus.) This allowed people to study the shallow floors more efficiently than snorkel or “hard hat” divers.
In the 1960s, Cousteau developed habitats in which “aquanauts” could stay underwater for weeks. His 1964 film “World Without Sun” won an Academy Award.
Shortly afterwards, the U. S. Navy carried out two successful underwater living experiments called “SEALAB.” A third attempt failed, and interest waned.
In 1960, the U. S. Navy and Swiss inventor Auguste Piccard completed development of the bathyscaphe “Trieste.” This “underwater balloon” took Jacques Piccard and Lt. Donald Walsh to the bottom of the Mariannas Trench. In their 20 minutes there, they proved that life can exist even in the greatest depths of the oceans.
Modern shipboard and airborne techniques for mapping the ocean floors include “side scan sonar” and high-resolution seismic profiling.
Magnetometers revealed that the oceanic basalts erupted at different times, in patterns that preserve a record of magnetic reversalsMagnetometers provide another important technique for understanding seafloor geology
Lamont vessels have been collecting samples from the ocean floor for more than half a century. The Deep-Sea Sample Repository houses the greatest collection of materials retrieved from the ocean floors.
The gravity piston corer has long been one of the basic tools used to collect samples of the sediments covering the sea bottom. “Doc” Ewing began the practice required all Lamont vessels to collect at least one core each day back in the late ’40s.
LDEO houses the East Coast Core Repository. The Borehole Group is the center for such drilling research here.